Allergic emergencies, such as anaphylaxis, are a growing concern, given the increasing awareness of members of the public of their frequency and potential severity. Anaphylaxis is a sudden, severe, systemic allergic reaction can be fatal, in many cases, if left untreated. Anaphylaxis can involve various areas of the body, such as the skin, respiratory tract, gastrointestinal tract, and cardiovascular system. Acute symptoms occur from within minutes to two hours after contact with the allergy-causing substance; but in rare instances onset may be delayed by as much as four hours. Contact with anaphylaxis-inducing agents, and the severity of the resulting anaphylactic reaction, can be extremely unpredictable. Accordingly, allergists recommend that persons who have a personal or family history of anaphylaxis be prepared to self-administer emergency treatment at all times. Additionally, adults charged with caring for children who are at risk for anaphylaxis should also be prepared to administer anti-anaphylactic first aid.
The symptoms of anaphylaxis include one or more of the following, generally within 1 to about 15 minutes of exposure to the antigen: agitation, a feeling of uneasiness, flushing, palpitations, paresthesias, pruritus, throbbing in the ears, coughing, sneezing, urticaria, angioedema, difficulty breathing due to laryngeal edema or brochospasm, nausea, vomiting, abdominal pain, diarrhea, shock, convulsions, incontinence, unresponsiveness and death. An anaphylactic reaction may include cardiovascular collapse, even in the absence of respiratory symptoms.
According to the Merck Manual, immediate treatment with epinephrine is imperative for the successful treatment of anaphylaxis. Merck Manual, 17th Ed., 1053-1054 (1999). The recommended dose is about 0.01 mL/Kg in adults: usually about 0.3 to 0.5 mL of a 1:1000 dilution of epinephrine in a suitable carrier. While the dose may be given manually, either subcutaneously or intramuscularly, in recent years automatic injectors have become an accepted first aid means of delivering epinephrine. It is recommended that persons at risk of anaphylaxis, and persons responsible for children at risk for anaphylaxis, maintain one or more automatic epinephrine injectors in a convenient place at all times. It is further recommended that, if the symptoms of anaphylaxis persist after the first dose of epinephrine is injected, the patient should be treated with a second dose of epinephrine (about 0.3 mL of the 1:1000 dilution).
Automatic injectors, such as those disclosed in U.S. Pat. Nos. 5,358,489; 5,540,664; 5,665,071 and 5,695,472 (each of which are incorporated herein by reference in its entirety) are known. In general, all automatic injectors contain a volume of epinephrine solution to be injected. In general, automatic injectors include a reservoir for holding the epinephrine solution, which is in fluid communication with a needle for delivering the drug, as well as a mechanism for automatically deploying the needle, inserting the needle into the patient and delivering the dose into the patient. A specific prior art automatic injector is described in U.S. Pat. No. 5,695,472, which is incorporated herein in its entirety.
Automatic injectors for injection of epinephrine solution include automatic injectors covered by U.S. Pat. No. 4,031,893, which is incorporated by reference herein in its entirety. Exemplary injectors provide about 0.3 mL of epinephrine solution at about a concentration of either 0.5 or 1 mg of epinephrine per mL of solution (1:2000 or 1:1000, respectively). Each injector is capable of delivering only one dose of epinephrine and any epinephrine left in the automatic injector (generally about 90% of the original volume of epinephrine) is unavailable for delivery and must be discarded. Thus, if one needs a second dose of epinephrine after the first dose has been delivered, a second automatic injector must be employed. Moreover, if the automatic injector misfires (i.e. fails to deploy the needle, deploys the needle but fails to dispense a dose of epinephrine, etc.), there is no way to access the remaining epinephrine manually. Again, an additional automatic injector unit must be employed in such a situation.
Additionally, the available automatic injectors deliver a uniform volume of 0.3 mL of epinephrine to the patient, whether that patient is an adult or a child. The pediatric version delivers 0.3 mL of a 1:2000 dilution of epinephrine. This volume of medicine can present severe discomfort to smaller children, which can lead to poor patient compliance or non-compliance. Given the acute and potentially lethal threat presented by anaphylaxis, prompt and diligent patient compliance is a must.
Thus, there is a need for a method of treating anaphylaxis, wherein two doses of epinephrine may be delivered from the same device. There is further a need for a device adapted to deliver two doses of epinephrine to the same patient. There is also a need for a method of treating anaphylaxis in a person of less than about 15 Kg, wherein a smaller volume of epinephrine can be delivered to the patient. There is also a need for a device capable to delivering two such smaller doses to a patient of less than about 15 Kg.
The invention meets the foregoing needs and provides related advantages as well.